The overall objective of the studies outlined in the application is to obtain a quantitative and fundamental physicochemical understanding of the interactions of immune complexes (IC) with immunoadsorbents. Special emphasis will be placed upon (1) obtaining a basic understanding of the complex interactions in solution involving antigen, antibody complement, and various other plasma borne molecules; (2) defining and quantifying the reactions in solution between IC both reactive and non-reactive towards complement components; and (3) investigating the reactions occurring during immunosorption of immune complexes with a variety of receptor molecules bound to solid supports and with cells which have receptors for immune complexes. Techniques to be used include classical and dynamic light scattering. HPLC, radioimmumnoassays, and electron microscopy. Experiments will be carried out with model immune complexes and with immune complexes isolated from sera of feline leukemia virus-infected cats. The proposed research will enhance our understanding of IC formation and behavior in the presence of complement and specific blood cells, and may provide a rational basis for future development and design of immunoadsorption techniques which may be applied diagnostically or therapeutically to a variety of disease states.